P0C88: Hybrid/EV Battery Temperature Sensor I Circuit
What to do
Worth asking for the live temperature values to be read side by side rather than relying on codes. From sensor I onward the car does not compare neighbours, so a sensor drifting by a few degrees will not set a correlation code and will quietly cost charging speed and power instead.
What this code means
Battery temperature sensor I has a circuit fault.
The family's argument is at P0BC2: a battery does not have a temperature, so it is measured in many places, and a faulty reading changes what the car permits rather than merely misinforming it.
Sensor I is the first one outside the correlation chain, and the difference in how it can fail is real.
Sensors A to H are each compared against a neighbour, so a sensor that drifts slowly is caught while its reading is still plausible — the comparison notices before the absolute limits do. From I onward there is no such comparison. These sensors are checked only against absolute limits, which is a far coarser net: a sensor reading four degrees high is inside every limit it will ever be tested against, and nothing will say so.
Two practical consequences. A drifting sensor in the I–P group tends to surface late, and it surfaces as something else — a pack that derates earlier than it used to, charging that has slowed for no stated reason, or a cooling system apparently working harder than the weather justifies. And when the correlation codes are silent, that is not evidence those sensors are healthy — it is evidence they are not being cross-checked. Reading the live values side by side is the substitute, and it costs a scan tool session rather than a part.
Likely causes
Start here
- Faulty battery temperature sensor · specialist
- Corroded or loose connector · easy
Less common
- Damaged cell voltage sense harness · specialist
- Faulty battery pack sensor module · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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